Unable to edit password policy

Hi All,

I am facing very strange issue while editing Default Domain Policy -> Computer Configuration->Windows Settings->Security Settings->Account Policies-> Password Policy -> Enforce password history

Whenever i try to edit the policies - i am getting the below error. 



Forest functional level:

Windows Server 2003

Domain functional level:

Windows Server 2008 R2.

I am a enterprise admin.

Is someone faced this problem already? Please help me to resolve this issue.

raja m